nose provides an alternate test discovery and running process for
unittest, one that is intended to mimic the behavior of py.test as much
as is reasonably possible without resorting to too much magic.

Basic usage

Use the nosetests script (after installation by setuptools):

nosetests [options] [(optional) test files or directories]

You may also use nose in a test script:

import nose
nose.main()

If you don't want the test script to exit with 0 on success and 1 on failure
(like unittest.main), use nose.run() instead:

import nose
result = nose.run()

result will be true if the test run succeeded, or false if any test failed
or raised an uncaught exception. Lastly, you can run nose.core directly, which
will run nose.main():

python /path/to/nose/core.py

Please see the usage message for the nosetests script for information
about how to control which tests nose runs, which plugins are loaded,
and the test output.

Features

Writing tests is easier

nose collects tests from unittest.TestCase subclasses, of course. But you can
also write simple test functions, and test classes that are not subclasses of
unittest.TestCase. nose also supplies a number of helpful functions for
writing timed tests, testing for exceptions, and other common use cases. See
Writing tests and Testing tools for more.

Running tests is easier

nose collects tests automatically, as long as you follow some simple
guidelines for organizing your library and test code. There's no need to
manually collect test cases into test suites. Running tests is also more
responsive, since nose begins running tests as soon as the first test module
is loaded. See Finding and running tests for more.

Setting up your test environment is easier

nose supports fixtures at the package, module, and test case level, so
expensive initialization can be done as infrequently as possible. See
Fixtures for more.

Doing what you want to do is easier

nose has plugin hooks for loading, running, watching and reporting on tests
and test runs. If you don't like the default collection scheme, or it doesn't
suit the layout of your project, or you need reports in a format different
from the unittest standard, or you need to collect some additional information
about tests (like code coverage or profiling data), you can write a plugin to
do so. See Writing plugins for more.

Output capture

Unless called with the -s (--nocapture) switch, nose will capture stdout
during each test run, and print the captured output only for tests that
fail or have errors. The captured output is printed immediately
following the error or failure output for the test. (Note that output in
teardown methods is captured, but can't be output with failing tests,
because teardown has not yet run at the time of the failure.)

Assert introspection

When run with the -d (--detailed-errors) switch, nose will try to output
additional information about the assert expression that failed with each
failing test. Currently, this means that names in the assert expression
will be expanded into any values found for them in the locals or globals
in the frame in which the expression executed.

Please note that dotted names are not expanded, and callables are not called
in the expansion.

Setuptools integration

nose may be used with the setuptools test command. Simply specify
nose.collector as the test suite in your setup file:

setup (
# ...
test_suite = 'nose.collector'
)

Then to find and run tests, you can run:

python setup.py test

When running under setuptools, you can configure nose settings via the
environment variables detailed in the nosetests script usage message.

Please note that when run under the setuptools test command, some plugins will
not be available, including the builtin coverage, profiler, and missed test
plugins.

nose also includes its own setuptools command, nosetests, that provides
support for all plugins and command line options, as well as configuration
using the setup.cfg file. See nose.commands for more information about the
nosetests command.

Writing tests

As with py.test, nose tests need not be subclasses of
unittest.TestCase. Any function or class that matches the configured
testMatch regular expression ((?:^|[b_.-])[Tt]est) by default)
and lives in a module that also matches that expression will be run as
a test. For the sake of compatibility with legacy unittest test cases,
nose will also load tests from unittest.TestCase subclasses just like
unittest does. Like py.test, functional tests will be run in the order
in which they appear in the module file. TestCase derived tests and
other test classes are run in alphabetical order.

Fixtures

nose supports fixtures (setup and teardown methods) at the package,
module, and test level. As with py.test or unittest fixtures, setup always
runs before any test (or collection of tests for test packages and modules);
teardown runs if setup has completed successfully, whether or not the test
or tests pass. For more detail on fixtures at each level, see below.

Test packages

nose allows tests to be grouped into test packages. This allows
package-level setup; for instance, if you need to create a test database
or other data fixture for your tests, you may create it in package setup
and remove it in package teardown once per test run, rather than having to
create and tear it down once per test module or test case.

To create package-level setup and teardown methods, define setup and/or
teardown functions in the __init__.py of a test package. Setup methods may
be named setup, setup_package, setUp, or setUpPackage; teardown may
be named teardown, teardown_package, tearDown or tearDownPackage.
Execution of tests in a test package begins as soon as the first test
module is loaded from the test package.

Test modules

A test module is a python module that matches the testMatch regular
expression. Test modules offer module-level setup and teardown; define the
method setup, setup_module, setUp or setUpModule for setup,
teardown, teardown_module, or tearDownModule for teardown. Execution
of tests in a test module begins after all tests are collected.

Test classes

A test class is a class defined in a test module that is either a subclass
of unittest.TestCase, or matches testMatch. Test classes that don't
descend from unittest.TestCase are run in the same way as those that do:
methods in the class that match testMatch are discovered, and a test case
constructed to run each with a fresh instance of the test class. Like
unittest.TestCase subclasses, other test classes may define setUp and
tearDown methods that will be run before and after each test method.

Test functions

Any function in a test module that matches testMatch will be wrapped in a
FunctionTestCase and run as a test. The simplest possible failing test is
therefore:

def test():
assert False

And the simplest passing test:

def test():
pass

Test functions may define setup and/or teardown attributes, which will be
run before and after the test function, respectively. A convenient way to
do this, especially when several test functions in the same module need
the same setup, is to use the provided with_setup decorator:

This will result in 4 tests. nose will iterate the generator, creating a
function test case wrapper for each tuple it yields. As in the example, test
generators must yield tuples, the first element of which must be a callable
and the remaining elements the arguments to be passed to the callable.

Setup and teardown functions may be used with test generators. The setup and
teardown attributes must be attached to the generator function:

The setup and teardown functions will be executed for each test that the
generator returns.

For generator methods, the setUp and tearDown methods of the class (if any)
will be run before and after each generated test case.

Please note that method generators are not supported in unittest.TestCase
subclasses.

Finding and running tests

nose, by default, follows a few simple rules for test discovery.

If it looks like a test, it's a test. Names of directories, modules,
classes and functions are compared against the testMatch regular
expression, and those that match are considered tests. Any class that is a
unittest.TestCase subclass is also collected, so long as it is inside of a
module that looks like a test.

Directories that don't look like tests and aren't packages are not
inspected.

Packages are always inspected, but they are only collected if they look
like tests. This means that you can include your tests inside of your
packages (somepackage/tests) and nose will collect the tests without
running package code inappropriately.

When a project appears to have library and test code organized into
separate directories, library directories are examined first.

When nose imports a module, it adds that module's directory to sys.path;
when the module is inside of a package, like package.module, it will be
loaded as package.module and the directory of package will be added to
sys.path.

Be aware that plugins and command line options can change any of those rules.

Testing tools

The nose.tools module provides a number of testing aids that you may
find useful, including decorators for restricting test execution time
and testing for exceptions, and all of the same assertX methods found
in unittest.TestCase (only spelled in pep08 fashion, so assert_equal
rather than assertEqual). See nose.tools for a complete list.

About the name

nose is the least silly short synonym for discover in the dictionary.com
thesaurus that does not contain the word 'spy'.

Similar test runners

nose was inspired mainly by py.test, which is a great test runner, but
formerly was not all that easy to install, and is not based on unittest.

Test suites written for use with nose should work equally well with py.test,
and vice versa, except for the differences in output capture and command line
arguments for the respective tools.

License and copyright

nose is copyright Jason Pellerin 2005-2007

This program is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.

You should have received a copy of the GNU Lesser General Public License
along with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA